There have been headphone devices each including a headband and a pair of speaker units joined to the respective end portions of the headband.
Among such headphone devices, there is a type of headphone device that can adjust the positions of the speaker units relative to the headband in accordance with the positions of the ears relative to the face, the size of the face, and the like (see Patent Document 1, for example).
In the headphone device disclosed in Patent Document 1, the headband has an expansion/contraction mechanism, and the headband expands and contracts to move the speaker units to the positions suitable for the ears of the user.
The expansion/contraction mechanism is formed with rollers, a cover for the headband, a stopper for maintaining a position determined as a result of expansion or contraction, and the like.